1. Field of the Invention
The present invention relates to an exhaust gas processing device.
2. Discussion of the Background
Many technologies are developed for purification (conversion) of an exhaust gas emitted from automobiles. However, increasing traffic is making countermeasures for the exhaust gas insufficient. On a global mass scale, automobile exhaust gas regulations are becoming strict.
In order to deal with the automobile exhaust gas regulations, catalytic agent carriers capable of processing predetermined toxic substances contained in the exhaust gas are used in an exhaust gas treatment system. A honeycomb structure is known as a member for the catalytic agent carrier.
The honeycomb structure includes plural cells (through holes) extending from one end surface of the honeycomb structure to the other end surface of the honeycomb structure in its longitudinal direction. The cells are formed in a honeycomb unit mutually separated by cell walls and carrying the catalytic agents. Therefore, if the exhaust gas passes through the honeycomb structure, the catalytic agent carried on the cell wall may convert (oxidize or reduce) materials such as a hydrocarbon compound (HC), carbon monoxide (CO), nitrogen oxide (NOx) and so on contained in the exhaust gas to treat the components in the exhaust gas.
The cell wall (base material) of the honeycomb unit forming the above honeycomb structure may be made of cordierite. A catalytic agent carrying layer made of γ-alumina is formed on the cell wall. A noble metal catalytic agent such as platinum, rhodium, platinum and rhodium, and so on is carried on the catalytic agent carrying layer.
Further, a honeycomb unit made of a material having a lower electrical resistivity such as silicon carbide than that of cordierite may be used in order to enhance an exhaust gas processing capability at a temperature lower than a temperature causing the catalytic agent to be active. An electrode for applying a voltage is provided in the honeycomb structure and electric power is applied to the honeycomb structure to heat the honeycomb structure according to Japanese Utility Model Application Publication No. 49-124412.
The entire contents of which Japanese Utility Model Application Publication No. 49-124412 are incorporated herein by reference.